Hormonal changes that occur when mice eat significantly less may help explain an already established phenomenon: a low calorie diet can extend the lifespan of rodents. And that's a benefit that even regular exercise does not achieve.
A study called “Effect of exercise and calorie restriction on biomarkers of aging in mice,” published in the May issue of the American Journal of Physiology being lean rather than obese is protective from many diseases.
"But key rodent studies tell us that being lean from eating less, as opposed to exercising more, has greater benefit for living longer,” said Derek M. Huffman, the study’s lead author. "This study was designed to understand better why that is."
Huffman cautions that the study applies only to rodents, which are different in some key ways from humans. However, at least two studies which examined people who engage in high-volume exercise versus people who restricted their calorie intake, - ie ate a low calorie diet - had a similar outcome: caloric restriction has physiological benefits that exercise alone does not.
Researchers expect that clues to the physiology of longevity in mice will eventually be applied to people, Huffman said.
Low Calorie Diet Idea Not New
The study built upon previous studies that showed:
Taken together, these findings indicate that caloric restriction protects against disease better than exercise does, and has the added benefit of extending the life span of some rats. Physiologists have been trying to unravel the reasons for this, and two major theories have emerged.
One theory is that exercise places stress on the body, which can result in damage to the tissues and DNA. Another theory is that a low calorie diet leads to physiological changes which benefit the body.
Huffman and his colleagues designed a study to examine the roles of exercise and caloric restriction, singly and combined. They controlled for factors such as weight and the amount of energy expended versus the calories consumed.
Overall, these findings indicate that the physiological stress of exercise did not produce enough damage to tissues or DNA to explain why exercise does not lengthen life span. Instead the study suggests that caloric restriction creates beneficial changes in the body’s hormone levels which exercise does not. The researchers concluded that these metabolic changes play a role in extending life.
A handful of studies comparing calorie restricted people to people who are avid exercisers, found similar hormonal benefits among those eating less. However, calorie restriction studies are difficult to carry out in people because participants often complain of feeling hungry, lethargic, and cold.
Huffman also emphasized that the benefits of exercise may be greater for humans than for mice because people are more prone to develop cardiovascular diseases, and exercise is particularly good at warding off those diseases. Mice tend to die of kidney disease and cancer, Huffman said.
“I wouldn’t say this study has direct implications for people right now,” Huffman said. “But it shows what physiological changes caloric restriction and exercise produce. We can continue to build upon these findings until we can get a better understanding of how this works in people.”
Anyone for a low calorie diet?